1. Field of the Invention
The present invention is in the field of crop harvesting equipment such as combines and harvesters.
2. Related Art
Agricultural machines such as combines and harvesters use headers to cut crop and move it into the machine for processing. The headers can be raised and lowered to cut the crop at various heights. Many headers are equipped with ground sensors that contact the ground as the header moves through a field during harvest. As the ground terrain changes the sensors move up and down in response. A potentiometer measures the angle of change of the ground sensors and continually sends an electric voltage to a computer controller which moves the header according to the signals from the ground sensors' constant contact with the ground contour. This keeps the header at a user selected height automatically.
There is a wide range of cutting heights that are desirable. Mechanical configurations for ground sensors that work well for higher heights, for example 400 millimeters, do not work well at lower heights in common usage, for example 25 millimeters, and vice versa.
Separately, it is advantageous for the sensor ground contact position to be very close to the cutter bar, at the leading edge of the header. This position close to the cutter bar allows the header to react quickly to changing ground contours. In the prior art long sensors mounted near the front of the header and near the cutter bar worked well for high cutting heights but, when the cutting height was lower, the long sensor arms, which move around a pivot mount, would contact the ground at a position too far to the rear of the cutter bar to respond quickly to changes in ground contour. Thus, long ground sensor arms did not work well for short cutting heights. Short ground sensor arms were advantageously responsive at short cutting heights, but would not reach the ground at all at high cutter heights.
Moreover, a short straight ground sensor mounted close to the cutter bar risked breakage when the operator backed the machine up with the sensor in its down position. The short sensor could also be broken if the operator lowered the header without simultaneously moving the machine forward. This double motion was not guaranteed.